--- title: "Reloop vs Plunk (2026): Open-Source Email Platforms Compared" description: "Reloop vs Plunk, two open-source email platforms compared: hosted pricing, licenses, self-hosting requirements, sending infrastructure, inbound email and automations, plus how to switch." canonical: "https://reloop.sh/blog/reloop-vs-plunk" last-updated: "2026-10-25" --- # Reloop vs Plunk (2026): Open-Source Email Platforms Compared > For the site documentation index, see [llms.txt](/llms.txt). Docs index: [llms-docs.txt](/llms-docs.txt). Marketing corpus: [llms-full.txt](/llms-full.txt). Docs corpus: [llms-full-docs.txt](/llms-full-docs.txt). Product skill: [skill.md](/skill.md). Prefer markdown URLs (append `.md`) when available. > Reloop vs Plunk, two open-source email platforms compared: hosted pricing, licenses, self-hosting requirements, sending infrastructure, inbound email and automations, plus how to switch. Source: https://reloop.sh/blog/reloop-vs-plunk Published: 2026-10-25 **Reloop and Plunk are both open-source email platforms that do more than send.** Each gives you a transactional API, SMTP, contacts, campaigns, automations and inbound email, on a hosted cloud or on your own server. The differences are in the details: **Plunk sends through Amazon SES and charges per email with no plan tiers; Reloop runs its own MTA, costs less once you pass a few thousand emails, and stores inbound mail in real inboxes that agents can work from.** Plunk's pricing is the simplest in the market, and its AGPL license is a deliberate choice worth understanding. We build Reloop, so weigh this accordingly. Plunk facts below come from [Plunk's pricing page](https://www.useplunk.com/pricing), [docs](https://docs.useplunk.com) and [GitHub repository](https://github.com/useplunk/plunk). Where Plunk is the better pick, we say so. --- ## The 30-second comparison | | **Reloop** | **Plunk** | |---|---|---| | License | Apache 2.0 | AGPL-3.0 | | Free tier | 3,000 / mo, 100 / day | 1,000 / mo, with Plunk branding | | Paid pricing | Plans: $10 for 50k, $20 for 100k | $0.001 per email, no base fee | | 50,000 emails / mo | **$10** | about $50 | | 100,000 emails / mo | **$20** | about $100 | | Dedicated IP | Included on Growth ($20) | Not offered on the hosted plan | | Sending path | Own MTA (KumoMTA) | Amazon SES | | Self-host needs | Your server | Your server + an AWS SES account | | Transactional API and SMTP | Yes | Yes | | Contacts, segments, campaigns | Yes | Yes | | Automations | Event-triggered, with delays and conditions | Workflows with triggers, delays and conditions | | Inbound email | Mailboxes with threads, API, MCP, IMAP | Inbound with routing rules | | Agent inbox | Yes | No | Plunk's prices are from [useplunk.com/pricing](https://www.useplunk.com/pricing); Reloop's are on [reloop.sh/pricing](/pricing). Both change, so check before you commit. --- ## Pricing at real volumes The two products price in different ways. Plunk charges a flat **$0.001 per email** (that's $1 per 1,000) with no base fee and no plan tiers, plus a free tier of 1,000 emails a month that carries Plunk branding. Reloop has a free tier of 3,000 a month, then flat plans with overage. | Monthly volume | Reloop | Plunk (approx.) | |---|---|---| | 1,000 | $0 | $0 (branded) | | 3,000 | $0 | about $3 | | 50,000 | $10 | about $50 | | 100,000 | $20 | about $100 | | 200,000 | $20 + $50 overage = $70 | about $200 | Plunk figures are per-email list price, rounded; check Plunk's page for exactly how the free allowance applies once you upgrade. What this means in practice: - **At very low or spiky volume, Plunk's model is hard to beat for simplicity.** You never pay for capacity you don't use, and Plunk offers a monthly spend cap. - **At steady volume, Reloop is cheaper.** From about 10,000 emails a month on, a Reloop plan costs less than the same mail at $1 per 1,000. - **On both, self-hosting removes the platform fee.** On Plunk you still pay AWS for SES sending. On Reloop you pay for the server only. Price the volume you expect in a year, not today's. Moving providers later means re-verifying DNS and rebuilding reputation, so pick the one that still makes sense at 10× your current volume. --- ## Open source: Apache 2.0 vs AGPL-3.0 Both projects publish their full source, but the licenses behave differently. - **Plunk is AGPL-3.0.** You can self-host and modify it freely. If you modify Plunk and let others use it over a network, the AGPL requires you to share those modifications under the same license. For a company running it internally that's often fine; for one embedding it in a product, check with your legal team. - **Reloop is Apache 2.0.** It's a permissive license: you can modify it, embed it and run it as part of a commercial product without publishing your changes, as long as you keep the license and notices. Neither is "more open". They make different trade-offs, and AGPL is a reasonable choice for a project that wants improvements to flow back. --- ## Self-hosting: what you actually run This is the biggest technical difference. **Plunk is built on Amazon SES.** Its [self-hosting guide](https://docs.useplunk.com/self-hosting/introduction) lists Docker and Docker Compose, a domain with subdomains for each service, and an AWS SES account. The [environment variables](https://docs.useplunk.com/self-hosting/environment-variables) mark PostgreSQL, Redis and the SES credentials as required, and the bundled setup includes MinIO for file storage. In practice that means: 1. Getting your AWS account out of the SES sandbox, which AWS reviews by hand. 2. Creating an IAM user for sending and domain identities. 3. Wiring an SNS topic and configuration set so bounces, complaints and deliveries flow back to Plunk. **Reloop brings its own MTA.** Reloop sends through KumoMTA running on your server, so there's no third-party sending account to apply for. You install it with the [one-command installer](/self-host) or on [Coolify](/blog/reloop-coolify-setup), point DNS at it, and send. The trade-off cuts both ways: | | Reloop self-hosted | Plunk self-hosted | |---|---|---| | Sending infrastructure | Your own IPs via KumoMTA | Amazon SES | | IP reputation | You own it and warm it up | SES handles it | | Extra cloud account | None | AWS (SES, IAM, SNS) | | Per-email cost | None | SES rates | | Data stays on your server | All of it | App data yes; mail passes through SES | If you'd rather not think about IP warm-up at all, SES doing the sending is a genuine advantage for Plunk. If you want no dependency on AWS, or mail that never leaves your infrastructure, Reloop's model fits better. Our [self-hosted email infrastructure guide](/blog/self-hosted-email-infrastructure) covers what owning IP reputation really involves. --- ## Developer experience Both APIs are small and easy to call. **Plunk** ```typescript const res = await fetch("https://next-api.useplunk.com/v1/send", { method: "POST", headers: { Authorization: `Bearer ${process.env.PLUNK_SECRET_KEY}`, "Content-Type": "application/json", }, body: JSON.stringify({ to: "user@example.com", subject: "Welcome", body: "

Thanks for signing up.

", }), }); ``` **Reloop** ```typescript const reloop = new Reloop({ apiKey: process.env.RELOOP_API_KEY! }); const { response, emailError } = await reloop.mail.send({ from: "Acme ", to: "user@example.com", subject: "Welcome", html: "

Thanks for signing up.

", }); ``` | | Reloop | Plunk | |---|---|---| | Auth | `x-api-key` header or SDK | `Authorization: Bearer` with a secret key (`sk_`) | | HTML field | `html` | `body` | | Template variables | `{{{first_name}}}` | `{{ firstName }}`, values in `data` | | Event tracking | `reloop.automations.start({ event, email })` | `POST /v1/track` with `event` and `email` | | Errors | `message`, `why` and `fix` | Error codes | | Webhooks | Signed with `Reloop-Signature` (HMAC-SHA256) | See Plunk docs | Plunk has a nice touch for frontend use: public keys (`pk_`) can only call `/v1/track`, so you can track events from the browser without exposing a sending key. Reloop's error shape is our one strong opinion. When a send fails, the error says **why** and **how to fix it**: ```json { "message": "Domain not found", "why": "The domain mail.acme.com was not found or is not authorized for your organization", "fix": "Ensure the domain is registered and verified in your dashboard" } ``` --- ## Automations, campaigns and contacts Here the two are closer than any other pair we've compared. Both cover: - **Contacts** with custom fields and activity history. - **Segments or groups** to target part of your list. - **Campaigns** for newsletters and product updates. - **Event-triggered automations** with delays and conditional branches. Both start an automation the same way: your app sends an event (`user.signed_up`) with the contact's email, and the contact is created if it doesn't exist. See our [welcome sequence guide](/blog/welcome-email-sequences-that-convert) for a worked example on Reloop. Reloop also has **subscription channels**, so a contact can opt out of product updates while still getting billing mail. --- ## Inbound email and agent inboxes Both can receive email on your domain. - **Plunk** receives inbound mail and processes it with routing rules. - **Reloop** receives mail into **mailboxes**: messages are stored, threaded, spam-scored with Rspamd, and readable over the API, the [MCP server](/docs/integrations/ai-tools/mcp-server) or IMAP. You can reply in-thread with one call. If you're building an AI agent that reads and answers email, or a shared inbox where humans and agents work the same threads, Reloop's mailboxes save you building storage and threading yourself. See [build an AI agent that reads and replies to email](/blog/build-ai-agent-sends-emails). --- ## Where Plunk is the better choice - **Your volume is low or unpredictable.** Paying $1 per 1,000 emails with no base fee and a spend cap is as simple as pricing gets. - **You want SES to own deliverability when self-hosting.** No IP warm-up, no MTA to tune; Amazon handles the sending reputation. - **You prefer AGPL** so that improvements to the platform stay open. - **You track events from the browser.** Plunk's public `pk_` keys are scoped to tracking only. ## Where Reloop is the better choice - **You send more than about 10,000 emails a month.** Flat plans ($10 for 50k, $20 for 100k) cost a fraction of per-email pricing. - **You want a larger free tier** without branding: 3,000 a month. - **You want to self-host without AWS.** Reloop sends with its own MTA, so there's no SES sandbox review or SNS wiring. - **You need inbound mail as real inboxes**, especially for AI agents over MCP or IMAP. - **You need a dedicated IP** on the hosted plan. - **You want a permissive license** to embed the platform in your own product. --- ## Switching from Plunk to Reloop 1. **Add your domain in Reloop** and publish the DKIM record (`reloop._domainkey`). Merge `include:reloop.sh` into your existing SPF record rather than adding a second one. 2. **Swap the send call.** Replace `POST /v1/send` with `reloop.mail.send`, and rename `body` to `html`. 3. **Move templates.** Change `{{ firstName }}` placeholders to triple braces: `{{{first_name}}}`. 4. **Swap event tracking.** Replace `/v1/track` calls with `reloop.automations.start({ event, email })`, and recreate your workflows as Reloop automations listening for the same event names. 5. **Import contacts** with their custom fields, and import unsubscribes so you never mail someone who opted out. 6. **Point webhooks** at a handler that verifies the `Reloop-Signature` header. 7. **Ramp traffic** from 10% to 100% over a week or two, then remove the old DNS records. Our [SendGrid migration guide](/blog/migrating-from-sendgrid) covers the same steps in more detail, including a traffic-split flag and a suppression import script. --- ## FAQ Yes. Reloop is Apache 2.0 and Plunk is AGPL-3.0. Both can be self-hosted with Docker. The main practical difference is that AGPL requires you to share modifications if you offer a modified version over a network. Yes. Plunk's self-hosting guide requires an AWS SES account for sending, along with PostgreSQL and Redis. Self-hosted Reloop sends through its own MTA, so no AWS account is needed. It depends on volume. Plunk charges $0.001 per email with no base fee, so it's cheap for tiny or irregular volumes. From around 10,000 emails a month, Reloop's plans cost less: $10 for 50k and $20 for 100k. Yes. Plunk processes inbound mail with routing rules. Reloop stores it in threaded mailboxes you can read over the API, MCP or IMAP, and reply to in one call. The HTML does. Change the placeholders from `{{ firstName }}` to `{{{first_name}}}` and pass the values as template variables.